Numerical and experimental techniques were used to characterize aerosol penetration through bends. Agreement between numerical and physical experiments was achieved when the numerical approach was based on the use of a specially developed three-dimensional particle tracking technique. It is also demonstrated that turbulence needs to be included in a particle tracking model. The effect of flow Reynolds number upon particle deposition was examined numerically. Results show that it affects aerosol penetration somewhat; however, it does not appear sufficiently significant to warrant inclusion in any correlation model. For Stokes numbers of 0.07-0.7 and a curvature ratio of 10, the aerosol penetration does not change by more than 5% when the Reynolds number is varied from 3200 to 19 800. Physical experiments were conducted to investigate the effect of curvature ratio on aerosol penetration. The bends were constructed such that each bend had the same initial and final spatial co-ordinates, regardless of the curvature ratio. ANSI N13.1-1969 recommends that the curvature ratio should be at least 10, but the results of this study suggest that the value could be 4. When bends are fabricated from straight tubing, there is a tendency for the tubing to flatten. The effect of flattening on aerosol penetration was tested by pinching bends at the 45°location, with degrees of flattening from 0% to 50%. If the degree of flattening is less than about 25%, it does not have a substantial impact on aerosol penetration. Numerical experiments were carried out to characterize the penetration of aerosols through bends. The geometrical extent of the bends covered only the region of tubing where the radius of curvature is finite. Results were used to generate a correlation model that designers and users of aerosol transport systems can employ to predict aerosol penetration. The correlation model is valid for the range of Stokes numbers between 0.07 and 1.2, for bend angles from 45°to 180°, and for curvature ratios from 2 to 10.
If dispersal occurs from an explosive radiological dispersal device, first responders need to know what actions they need to take to protect life and property. Many of the decisions required to minimize exposure will be made during the first hour. To help the first responder decide what countermeasures to employ, Sandia National Laboratories has established realistic hazard boundaries for acute and sub-acute effects relevant to radiological dispersal devices. These boundaries were derived from dispersal calculations based on the aerosolization behavior of devices tested in the Sandia Aerosolization Program. For 20 years, the Sandia Aerosolization Program has performed explosive and non-explosive aerosolization tests relevant to radiological dispersal devices. This paper discusses (1) the method and technical bases used to establish hazard boundaries and the appropriate actions that apply within those areas and (2) whether large-scale evacuations or sheltering in place are appropriate responses to a radiological dispersal device event.
Ignition experiments from various sources, including our own laboratory, have been used to develop a simple ignition model for pentaerythritol tetranitrate (PETN). The experiments consist of differential thermal analysis, thermogravimetric analysis, differential scanning calorimetry, beaker tests, one-dimensional time to explosion tests, Sandia's instrumented thermal ignition tests (SITI), and thermal ignition of nonelectrical detonators. The model developed using this data consists of a one-step, first-order, pressure-independent mechanism used to predict pressure, temperature, and time to ignition for various configurations. The model was used to assess the state of the degraded PETN at the onset of ignition. We propose that cookoff violence for PETN can be correlated with the extent of reaction at the onset of ignition. This hypothesis was tested by evaluating metal deformation produced from detonators encased in copper as well as comparing postignition photos of the SITI experiments.
The objective of this subtask of the Unconventional Nuclear Warfare Design project was to demonstrate mitigation technologies for radiological material dispersal and to assist planners with incorporation of the technologies into a concept of operations.The High Consequence Assessment and Technology department at Sandia National Laboratories (SNL) has studied aqueous foam's ability to mitigate the effects of an explosively disseminated radiological dispersal device (RDD). These benefits include particle capture of respirable radiological particles, attenuation of blast overpressure, and reduction of plume buoyancy. To better convey the aqueous foam attributes, SNL conducted a study using the Explosive Release Atmospheric Dispersion model, comparing the effects of a mitigated and unmitigated explosive RDD release. Results from this study compared health effects and land contamination between the two scenarios in terms of distances of effect, population exposure, and remediation costs.Incorporating aqueous foam technology, SNL created a conceptual design for a stationary containment area to be located at a facility entrance with equipment that could minimize the effects from the detonation of a vehicle transported RDD. The containment design was evaluated against several criteria, including mitigation ability (both respirable and large fragment particle capture as well as blast overpressure suppression), speed of implementation, cost, simplicity, and required space. A mock-up of the conceptual idea was constructed at SNL's 9920 explosive test site to demonstrate the containment design.-4- AcknowledgmentPaul Johnson, Mark Naro, and Weldon Teague from Sandia National Laboratories were an integral part of the development team. Without their hard work, we would not have had the mock-ups necessary to demonstrate our design ideas.
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